Newton famously said, “If I see further than others, it is by standing on the shoulders of giants.” However, for 3D printing, it could be the other way around. If one printer prints larger than others, it is probably using work developed for smaller printers. There are a variety of very large 3D printers out now and you often see claims in the press of “the world’s largest 3D printer”. Roboze, for example, makes that claim with a build volume of 1 meter on each axis.
I don’t dispute them, but depending on your definitions, there are FDM printers with higher volume capacity. There are also plenty of other machines claiming roughly the same size, from 3D Platform’s WORKBENCH XTREME to re:3D Terabot. Of course, all of these come with a great price. But we have even seen a home printer with an 800mm x 500mm bed. Also, infinity bed printers are not that uncommon, although they do have some limitations. In particular, they are usually only large on one axis.
Then there are the big industrial machines that print things like houses, bridges, and ships. The University of Maine, for example, has a large printer that has a 100-foot bed and prints about 500 pounds of plastic per hour. All that for just $2.5 million. You can see from the video below that part cooling is done in a rather unique way on that printer.
Problems
It’s easy to think that if you can make a printer that can print the size of a postcard, you should be able to scale it down to card stock without too much trouble. But that is not the case. Let’s focus on Cartesian-style printers.
You basically have a few options. You can move the bed, you can move the printhead, or you can have a combination. For example, many printers move the head in the X and Z direction and then move the bed in the Y direction. Others move the bed in the Z direction and move the head in X and Y. This latter scheme is especially popular for mechanical XY center.
So let’s start with the bed. If it moves, a large bed will be heavy. It’s also harder to get a good flatbed as you get bigger. It’s okay. Just keep the bed still somewhere other than the Z axis, then, right? It probably also requires heating. If you’ve ever had a cheap printer with a poor power supply, you know that even heating a 150mm bed can be a challenge. Unlike the heat block, you’re trying to get a fairly large area that radiates heat to stay warm. When you multiply the size, you multiply that problem. To reduce the load on the power supply, maybe opt for an AC heater.
The bed also has to support more weight. Granted, for any reasonably sized printer, the extra plastic probably won’t be too heavy, but if you were doing something giant or printing on a dense material (like concrete), that might be another problem. Plus, we’ve seen a 3D printed part already weigh over 1,500 pounds, so think big. Also, if the bed is moving in the Z axis, that system has to lift the largest bed with the heaviest heaters on board.
Speaking of beds, leveling a large bed will be even more of a hassle than it is today, though auto-leveling can help with that. Another thing that can be worse is warping. Larger parts will have more force as they contract.
Rigidity
A bed that doesn’t move will be easier to hold, but still has the mechanism to support the head. Some very small printers use a cantilever arm to support the printhead, but even most full-size printers support both ends. At some point the head will need bigger rails or rods or whatever you are using to support it.
Of course, any alignment issues also increase as you get older. That 0.5mm deviation at 200mm will be much wider at 1 meter. Errors of any kind will add up, of course. A little wobble on a Z axis rod or a little slip on a belt will add up as the travel increases.
hot end issues
Assuming you’re not going to do something weird like zone the print bed, you should also consider the hot end. We no longer like to wait for 3D prints on our normal printers. A giant printer probably needs a larger nozzle and very high flow rates to increase print speed. But that requires more temperature. Some of the newer hotends are made for high flow and even heating, but this will be a bigger concern with a very large printer. But consider the University of Maine press. Uses a 10mm nozzle to produce 12.5mm lines in 5mm layers.
Speaking of high flow, if you’re really aiming at a large object, there’s another concern: material supply. If it’s feeding a reel, will it run out? Again, the huge printer takes granules, which makes sense. You just have to keep the hopper full.
One answer, of course, is to use more than one hotend, although that has its own problems. We saw a 5 head machine in 2017.
design trades
Making trade-offs is a fundamental part of engineering. We want safe cars, but buying and operating an indestructible car would be expensive. So you make tradeoffs. The same goes for the design of a large printer.
Of course, we have already made a fundamental decision that you could review: we are using a normal FDM printer. A robotic arm or SCARA printer would be another option, though it would just have to make a different set of trade-offs. There is no perfect solution. Perhaps the really big printers are mobile robots that straddle their to this build plate, rising from the ground or descending from above?
What are your plans to make a giant printer? If you want detailed inspiration, there is this master’s thesis detailing the construction of a great printer. The cost was a few thousand dollars, but that included some donated material. Of course, your current printer can print huge objects. Just not all at once. Whatever you do, be sure to let us know so we can help you share your design.
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